Abstract With the growing rate of Alzheimer?s disease and nominal medication effects comes the need for novel treatment approaches. Transcranial direct current stimulation (tDCS) is a method of non-invasive brain stimulation that uses low intensity electric currents to alter the excitability of the brain. Initial evidence suggests that tDCS may improve cognitive functioning in patients with mild cognitive impairment (MCI) and Dementia - Alzheimer?s Type (DAT). The Stimulation to Improve Memory (STIM; R01AG058724) study directly addresses three key knowledge gaps about the fundamental preconditions for tDCS use: 1) who benefits, 2) how much electrical current is needed and, 3) for how long is treatment needed? The study randomizes participants across the clinical spectrum of MCI to DAT to receive between five and 30 consecutive daily sessions of HD- tDCS at either sham, 1 milliamp (mA), 2mA, or 3mA over the lateral temporal cortex ? using neurophysiological change (functional magnetic resonance imaging - fMRI) as the primary outcome measure. Participants complete weekly neuropsychological testing in order to establish dose-response curves and identify optimal treatment parameters. STIM is also the first tDCS study to integrate the amyloid, tau, neurodegeneration (A/T/N) framework, specifically by using MRI to quantify brain volume and positron emission tomography (PET) ligands to measure beta-amyloid and neurofibrillary tau. STIM participants, mirroring broader public needs, have voiced strong and compelling interest about learning the results of their personal PET amyloid and tau biomarker scans. The proposed ethics supplement addresses three ethical dilemmas underlying the communication gap in Alzheimer?s Disease (AD) biomarker research: 1) the withholding of biomarker information from interested participants, 2) the unknown ability of cognitively symptomatic patients to appreciate risks and benefits of biomarker disclosure, and 3) the psychological ramifications of biomarker disclosure in cognitively impaired patients. We will leverage STIM infrastructure to accomplish three specific aims. Aim 1 assesses both interest in, and actual receipt of, amyloid and tau PET disclosure in individuals with MCI and DAT. All participants enrolled in STIM will be offered this information, and both initial interest in and actual participation in biomarker disclosure will be tracked and compared by diagnosis. Aim 2 will evaluate whether interested participants, or their legally authorized representatives (LARs), are able to demonstrate decisional capacity for biomarker disclosure, and whether decisional capacity varies by diagnosis. Interested participants will receive psychoeducation about biomarker disclosure, a standardized assessment of decision- making capacity, and disclosure of their amyloid/tau status as appropriate. Aim 3 assesses both positive and negative psychological and behavioral reactions to disclosure, both shortly after receiving the information as well as a longer-term follow-up. Regardless of outcome, the results will address a vital knowledge gap about biomarker disclosure in cognitively symptomatic older adults.